Beyond Lorentz Force: Electron Circles in Magnetic Field?

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Discussion Overview

The discussion revolves around the behavior of electrons in a magnetic field, particularly focusing on the implications of the Lorentz force and whether electrons move in circular paths when subjected to such forces. The scope includes conceptual clarifications and technical explanations related to the motion of electrons in wires versus free electrons in a magnetic field.

Discussion Character

  • Conceptual clarification
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that when a wire is placed in a magnetic field, the Lorentz force acts on electrons, causing them to change direction without a change in speed, leading to circular motion.
  • Others argue that while free electrons can move in circles in a magnetic field, electrons in a wire are constrained to follow the wire's path.
  • One participant suggests that if the force were not perpendicular to the velocity, it would result in an increasing force and velocity, which would violate the law of conservation of energy.
  • There is a clarification regarding the definition of velocity, with some participants emphasizing that a change in direction implies a change in the velocity vector, although the magnitude of the velocity may remain constant.
  • Another participant stresses the importance of using technical terms correctly to avoid confusion in discussions about physics concepts.

Areas of Agreement / Disagreement

Participants express differing views on the behavior of electrons in magnetic fields, particularly regarding the implications of the Lorentz force and the nature of velocity. The discussion contains both clarifications and corrections, indicating that there is no consensus on some aspects of the topic.

Contextual Notes

There are unresolved nuances regarding the definitions of velocity and the conditions under which electrons behave as described. The discussion reflects varying interpretations of the effects of magnetic fields on electron motion.

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When a wire is placed in a magnetic field, Lorentz force acts on an electron in a direction perpendicular to velocity and to the magnetic field, since the magnetic force is perpendicular to the velocity the electron will only change direction with no velocity change, what happens after that, I have heard that the electron will move in circles, is that true??
 
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A free electron moves in circles (assuming the field spreads out wide enough to cover that), but electrons in a wire cannot just leave that, so they follow the wire.
 
We can say that if the force was not perpendicular to the velocity will have an ever-increasing force and velocity
Violating the law of conservation of energy
 
ElmorshedyDr said:
the electron will only change direction with no velocity change

Just a very small point, but one which could cause you confusion… If the electron changes direction it's velocity is bound to change. That's because the velocity vector gives the direction of travel as well as the speed. [Velocity may be defined as the displacement (a vector) per unit time.] What you meant was that "the electron will only change direction with no speed change".
 
Philip Wood said:
Just a very small point, but one which could cause you confusion… If the electron changes direction it's velocity is bound to change. That's because the velocity vector gives the direction of travel as well as the speed. [Velocity may be defined as the displacement (a vector) per unit time.] What you meant was that "the electron will only change direction with no speed change".
I meant the magnitude of the velocity
 
I thought you probably did mean this, but using technical terms correctly is a good habit to get into.
 

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